Numerical investigation of design and operating parameter effects on permeability-differentiated alkaline fuel cell with metal foam flow field

Abstract

• Effect of design and operating parameters are investigated and optimized numerically. • Temperature and pressure have different effect in different current density regions. • Anode metal foam thickness has significant effect while cathode is negligible. • Lower anode and higher cathode permeability lead to better performance. • Permeability-differentiated layout of metal foam flow fields is originally proposed. Metal foam (MF) material is recognized as an attractive flow field for the alkaline anion exchange membrane fuel cell (AAEMFC). In this paper, the effect of design parameters (MF thickness and permeability) and operating parameters (operating temperature and back pressure) are investigated and optimized through the numerical study. The maximum temperature of the AAEMFC with MF flow field is lower and temperature distribution is more uniform compared to that of AAEMFC with serpentine flow field. In general, the higher operating temperature decreases the cell performance slightly in the low current density region but enhances the cell performance obviously in the medium and high current density regions. The higher back pressure promotes the cell performance in the low current density region but decreases the cell performance in the high current density region. The anode MF thickness has the significant effect on the cell performance, and the thinner anode MF thickness benefits the cell performance. However, the effect of cathode MF thickness is relatively negligible. The lower permeability of the anode MF and higher permeability of cathode MF lead to the better performance. The permeability-differentiated layout of MFs in anode and cathode sides is proposed for the first time, and it is proven to improve the cell performance effectively due to the enhanced hydraulic permeation and membrane hydration. Electrochemical kinetics, thermal and water transport characteristics (including pressure drop, liquid water transport, membrane water distribution and ohmic loss) are analyzed in detail to explain the cell performance improvement.